#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int m = 0,n=0;
		double sum1=1;
	scanf("%d", &m);
	for ( n = 1; n <= m; n++)
	{
		sum1 = n * sum1;
	}
	printf("%lf\n", sum1);
	return 0;
}